Now was that so hard?
Yes it was. Besides being dicey, you'd have to hold on to the communication as legal proof of the permission which in this case could possibly be the chatterbox messaging; html? screenshot? both so easily forged it's not even worth talking about. And it's not even possible to get that far all the time--there are lots of monks on permanent or semi-permanent sabbatical.
A drop down (with a note box too?) for selecting the license you want attached to your code is a really good idea.
Update: you could also have your default license in your user prefs which would automatically attach to snippets and CC submissions.